This project is concerned primarily with the physiology of vertebrate photoreceptors, the processing of visual information within the retina, and the mechanisms underlying retinal responses. Both intra- and extracellular recordings will be made from photoreceptors and retinal neurons in selected species. Specific problems to be investigated include: 1) Role of cyclic nucleotides in retinal neuronal function. 2) Effects of dopamine, cAMP and other substances on isolated retinal neurons. 3) Effects of photopigment bleaching on receptor physiology. 4) The physiological and pharmacological properties of bipolar cells.